The central objective of the study is to clarify the relationship between aggressive behavior, dominance rank and testosterone secretion in rhesus monkeys living in social groups. Dominance rank and presence of estrous state will be studied as potential stimuli influencing testosterone secretion. The effects of increased testosterone secretion on aggressive behavior will be assessed in two ways: 1) by observation of behavior following stimulation of adult gonadal secretion by administration of gonadotropins: 2) observation of behavioral changes associated with rising testosterone levels in puberty.